JP2004017458A - Ink jet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recorder capable of producing a high quality image having no color shift in the subscanning direction through a simple arrangement. <P>SOLUTION: A slit part 20 having slits at a constant interval is provided on a circle at the edge of a carrying belt 12. An encoder 13 reads out a synchronization signal by detecting presence of the slit at the edge of the carrying belt 12. The encoder 13 outputs the carrying speed of a sheet being carried on the carrying belt 12 as a synchronization signal pulse. Period of the pulse varies depending on the carrying speed of the carrying belt 12 read out by means of the encoder 13 and a print head 11 is driven in synchronism with the output signal pulse to eject ink thus printing on the recording sheet 1. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an inkjet recording apparatus, and more particularly, to an inkjet recording apparatus that conveys a print recording medium and forms an image thereon.
[0002]
[Prior art]
An ink jet recording apparatus that conveys a print recording medium and forms an image thereon includes an ink jet head (print head) and a motor-driven pulley, gear, belt, and the like that conveys the print recording medium to the print head. Transport means. In order to form an image at a predetermined position on the print recording medium, the print recording medium must be transported in synchronization with the timing at which ink is ejected from the print head.
[0003]
FIG. 6 is a schematic diagram showing an example of the configuration of an ink jet printer according to the related art. In the drawing, reference numeral 50 denotes an ink jet printer. The inkjet printer 50 includes a paper feed unit including a paper feed tray 56, a paper transport unit including a transport belt 52, a print head 51, a paper discharge unit, and the like.
[0004]
The paper feed unit supplies a print recording medium (hereinafter, referred to as paper) to the printer main body, and in addition to a paper feed tray 56 for setting paper, a pickup roller for feeding the set paper, and a paper feed roller for feeding paper. It is composed of a conveying roller and the like for guiding the cut sheet to a sheet conveying section. The paper transport unit includes a transport belt 52, a drive motor 55, a transport roller 54, a pulley, a gear, and the like, and transports the paper from the paper feed unit to the outlet of the inkjet printer 50 through the arrangement of the print head 51. In the configuration example illustrated here, the sheet conveyed from the sheet feeding unit is conveyed by the conveyance belt 52 in the printing direction. The transport belt 52 is charged by applying a high voltage, and the sheet is electrostatically attracted on the transport belt 52 by this charging, and is transported together with the transport of the transport belt 52. The transport belt 52 is driven by a drive motor 55.
[0005]
The print head 51 is fixed to the carriage and moves together with the carriage to discharge ink to form an image on paper. When the ink jet printer 50 has a full color specification, the print head 51 is formed of four color heads of a black head, a cyan head, a magenta head, and a yellow head in order to form a full color image. The paper discharge section stocks the paper on which the image is formed, and includes a paper discharge roller for guiding the paper to the paper discharge side, a paper discharge tray for storing the discharged paper, and the like.
[0006]
In order to form an image at a predetermined position on a sheet, a disk 57 is provided on a shaft of a roller 54 for conveying the sheet. A slit portion 60 provided with marks such as slits at equal intervals is provided at the circumferential edge of the disk 57, and an encoder sensor 53 that can read the marks such as slits as signals is attached. When printing is performed by matching the recording positions of the respective colors in the sub-scanning direction, the signal of the encoder sensor 53 is read and printing is performed in synchronization.
[0007]
However, in the above-described related art, the paper transport speed may be different for each product due to variations in the shape of the transport rollers 54, pulleys, gears, and the like that constitute the transport unit, and the paper is supplied by the paper feed unit. Although the sheet is transferred to the conveying means, the conveying speed varies depending on the position of the conveying belt, and the conveying speed of the sheet changes.
[0008]
Japanese Patent Application Laid-Open No. H11-170623 discloses a printing apparatus that employs a printing timing determination method different from that of the above-described inkjet printer 50. The printing apparatus employs an encoder that transmits rotation from a roller in contact with a conveyance belt. A printing apparatus that determines a printing timing by using a signal from an encoder that rotates with conveyance as a clock signal is described. The publication also discloses a printing apparatus in which an encoder acts on a drive shaft for driving a transport belt, detects a moving speed of the transport belt, and determines a printing timing.
[0009]
However, since the signal is not directly detected from the transport belt that moves with the sheet, the transport distance calculated from the detected signal is different from the actually transported distance. As a result, printing cannot be performed at an accurate position, color shift occurs in the sub-scanning direction, and image quality deteriorates.
[0010]
Further, in the publication, slits are provided at equal intervals (same as the resolution in the transport direction of the printer) on the entire circumference of the transport belt, and the reflected light of the light applied to the slit is detected to determine the passing speed of the slit. There is also described a printing apparatus provided with a belt speed sensor for calculating a conveyance distance by measuring the distance. This printing apparatus detects the leading edge of the conveyed paper with a paper sensor, counts the number of slits (clocks) of the conveyor belt with a belt speed sensor, and discharges the image based on the transferred image data and the number of clocks. To determine.
[0011]
However, a method of generating a synchronization signal from a signal from an encoder of a conveyance roller that drives the conveyance unit and performing printing based on the synchronization signal does not directly control printing using an output signal of the encoder. The transport distance calculated from the signal of the encoder differs from the actual transport distance. As a result, printing cannot be performed at an accurate position, color shift occurs in the sub-scanning direction, and image quality deteriorates.
[0012]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has an ink jet recording apparatus and a control method thereof capable of obtaining a high-quality image without color shift in the sub-scanning direction with a simple configuration. Its purpose is to provide.
[0013]
[Means for Solving the Problems]
According to a first aspect of the present invention, in the ink jet recording apparatus, a transport unit that transports a print recording medium, and a synchronization signal for controlling a print head according to a transport speed of the print recording medium that is transported by the transport unit are transmitted to the transport unit. And a control means for controlling a print head to print an image based on the synchronization signal read by the synchronization signal reading means.
[0014]
According to a second aspect of the present invention, in the first aspect, the transporting means has a transport belt for transporting a print recording medium, and the transport belt has slits provided at equal intervals on an edge of the transport belt. The synchronization signal reading means has a sensor for detecting the presence or absence of the slit and reading the synchronization signal.
[0015]
According to a third aspect of the present invention, in the second aspect, the sensor is an encoder that outputs a pulse as a synchronization signal of a transport speed of a print recording medium transported by the transport belt. .
[0016]
According to a fourth aspect of the present invention, in the second or third aspect, there is provided means for detecting the origin of the transport belt with the sensor.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
In the ink jet recording apparatus according to the present invention, the print head is directly fed from the conveying means for conveying the print recording medium so that a high-quality image having no color shift in the sub-scanning direction can be obtained with a simple configuration. A control synchronization signal is read, and the print head is controlled to print an image based on the read synchronization signal. Hereinafter, an embodiment of the present invention will be described using an example of an inkjet printer as an inkjet recording apparatus.
[0018]
FIG. 1 is a schematic view showing an example of the configuration of an ink jet printer according to an embodiment of the present invention. In the drawing, reference numeral 10 denotes an ink jet printer. The inkjet printer 10 includes a paper feed unit including a paper feed tray 16, a paper transport unit including a transport belt 12, a print head 11, a paper discharge unit, and the like.
[0019]
The paper supply unit supplies a print recording medium (hereinafter, referred to as paper) to the printer main body, and in addition to a paper supply tray 16 for setting paper, a pickup roller for feeding the set paper, and a paper feed roller for supplying paper. It is composed of a conveying roller and the like for guiding the cut sheet to a sheet conveying section. A paper transport unit as an example of a transport unit includes a transport belt 12, a drive motor 15, a transport roller 14, a pulley, a gear, and the like. The paper is transported from a paper feed unit to an outlet of the inkjet printer 10 through an arrangement unit of the print head 11. Is transported. In the configuration example illustrated here, the sheet conveyed from the sheet feeding unit is conveyed by the conveyance belt 12 in the printing direction. The conveyance belt 12 is charged by applying a high voltage, and the sheet is electrostatically attracted on the conveyance belt 12 by this electrification, and is conveyed together with the conveyance of the conveyance belt 12. The transport belt 12 is driven by a drive motor 15.
[0020]
The print head 11 is fixed to the carriage and moves together with the carriage, and discharges ink to form an image on paper. When the ink jet printer 10 has a full-color specification, the print head 11 includes four color heads of a black head, a cyan head, a magenta head, and a yellow head in order to form a full-color image.
[0021]
The transport belt 12 transports the paper 1 thereon to the paper start position, where the print head 11 moves in the main scanning direction and prints an image. When the printing for one line is completed, the transport belt 12, that is, the paper 1 is moved in the sub-scanning direction by the drive motor 15, and the printing for the next line is performed. Thus, printing is performed in the main scanning direction and the sub-scanning direction. The paper discharge unit is for storing paper on which an image is formed, and includes a paper discharge roller for guiding the paper to the paper discharge side, a paper discharge tray for storing the discharged paper, and the like.
[0022]
FIG. 2 is a diagram showing an outline of a conveyor belt in the ink jet printer of FIG. 1, and FIG. 3 is an enlarged view showing an outline of a slit provided on the conveyor belt of FIG.
The synchronizing signal reading means is means for directly reading a synchronizing signal for controlling the print head according to the conveying speed of the print recording medium conveyed by the conveying means from the conveying means. A slit portion 20 is provided on the circumference. As shown in FIG. 3, the slit section 20 has slits 22 provided at equal intervals, and the synchronization signal reading means has a sensor that detects the presence or absence of the slit 22 and reads a synchronization signal. The interval between the slits 22 is the same as the resolution in the sub-scanning direction of the ink jet printer, and the configuration is such that the ability to detect the amount of movement of the transport belt 12 is equal to the resolution. In the present configuration example, as an example of this sensor, an encoder 13 that outputs a pulse as a synchronization signal of the transport speed of the sheet 1 transported by the transport belt 12 at the edge of the transport belt 12 is attached to the printer main body. The encoder (also referred to as an encoder sensor) 13 can execute accurate position control in accordance with the actual transport speed.
[0023]
The slits 22 recorded at equal intervals on the conveyor belt 12 conveyed by the drive motor 15 are read by the encoder 13, and the period of the above-mentioned pulse changes according to the conveyance speed. As will be described later, the control means drives the print head 11 in synchronization with the pulse of the output signal to control the discharge of the ink and the printing on the recording paper 1.
[0024]
Further, it is preferable to provide a unit for detecting the origin of the transport belt 12 with a sensor such as the encoder 13. Here, the slits 22 are equidistant from the printing start position (origin), and are arranged so that the paper on the conveyor belt 12 can be always detected at a fixed position on the conveyor belt 12. For this reason, as shown in FIGS. 2 and 3, the slit portion 20 is not provided on the entire circumference of the conveyor belt 12, and the portion from the printing end position (end point) to the origin is not slit portion. It is preferably 21. Note that the intervals between the slits 22 are very close when the print head is a line head. By reading this interval with an encoder sensor, a signal synchronized with each line recorded by the line head can be obtained.
[0025]
Here, the sequence of ink ejection by the print head 11 will be described in detail. At the same time as detecting the leading edge of the conveyed sheet 1, the encoder 13 on the conveyor belt 12 is read and the number of pulses is counted. The ejection position of the image is determined by the transferred image data and the number of counted pulses. Since the number of pulses is equal to the resolution as described above, the subsequent image creation is performed by sending an ink ejection signal corresponding to the image signal to the print head 11 in synchronization with the detected pulse.
[0026]
FIG. 4 is a block diagram illustrating a control unit that controls a print head in the inkjet printer of FIG. Image data is transmitted from a personal computer (PC) 31, and an output signal from the encoder 13 is taken into a main control circuit 32. A trigger signal is generated based on this output signal, and a signal is sent to the head drive circuit 33 to instruct each inkjet head 34 to eject ink. The head drive circuit 33 also sends a control signal to the motor driver 35 of the motor 36 that drives the print head 11 at the same time.
[0027]
FIG. 5 is a timing chart showing the timing for driving the print head based on the output signal detected by the encoder in the ink jet printer of FIG.
First, the home position (origin) is detected by the encoder 13 as the origin signal 41, and the output signal of the encoder 13 is read. As the output signal of the encoder 13, pulses in which the phases of the A phase and the B phase are shifted (A phase output signal 42 and B phase output signal 43, respectively) are output. Normally, control is performed based on the A-phase output signal 42, but the B-phase output signal 43 is used when detecting the rotation direction. As described above, the print trigger is generated in synchronization with the pulse signal of the encoder 13, and the timing for driving the print head 11 is generated. The print trigger I (44) indicates a print trigger when the pulse of the encoder 13 is used as it is, and the print trigger II (45) indicates a print trigger when printing is performed by doubling the pulse of the encoder 13 to double the resolution. I have.
[0028]
In the present invention, a belt speed sensor based on a method of detecting reflected light and measuring a passing speed of a slit as in the related art is not provided, and for example, as described in FIG. 1 and FIG. By arranging a sensor such as the encoder 13 that can directly read the slit 22 of the belt 12, it is possible to form an image without color shift in the sub-scanning direction with a simple configuration. That is, a synchronization signal is read from the transport belt 12 that transports the paper 1 and printing of each color is performed in accordance with the actual transport speed, so that a high-quality image without color shift in the sub-scanning direction can be obtained.
[0029]
【The invention's effect】
According to the present invention, it is possible to obtain a high-quality image without color shift in the sub-scanning direction with a simple configuration.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration example of an inkjet printer according to an embodiment of the present invention.
FIG. 2 is a diagram showing an outline of a transport belt in the ink jet printer of FIG.
FIG. 3 is an enlarged view showing an outline of a slit provided on the conveyor belt of FIG. 2;
FIG. 4 is a block diagram showing a control unit for controlling a print head in the ink jet printer of FIG.
FIG. 5 is a timing chart showing a timing for driving a print head based on an output signal detected by an encoder in the inkjet printer of FIG. 1;
FIG. 6 is a schematic diagram illustrating an example of a configuration of an ink jet printer according to a related art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... paper, 10 ... inkjet printer, 11 ... print head, 12 ... transport belt, 13 ... encoder, 14 ... transport roller, 15 ... drive motor, 16 ... paper feed tray, 20 ... slit part, 21 ... non-slit part, Reference numeral 22: slit, 31: PC, 32: main control circuit, 33: head drive circuit, 34: inkjet heads, 35: motor driver, 36: motor, 41: origin signal, 42: A-phase output signal, 43: B Phase output signal, 44: print trigger I, 45: print trigger II.

Claims (4)

In an ink jet recording apparatus, a transport unit that transports a print recording medium, and a synchronous signal reading unit that directly reads a synchronous signal for controlling a print head according to a transport speed of the print recording medium transported by the transport unit from the transport unit. And an control unit for controlling a print head to print an image based on the synchronization signal read by the synchronization signal reading unit. The transport unit has a transport belt that transports a print recording medium, the transport belt has slits provided at equal intervals on an edge of the transport belt, and the synchronization signal reading unit detects the presence or absence of the slit. 2. The ink jet recording apparatus according to claim 1, further comprising a sensor for reading the synchronization signal. 3. The ink jet recording apparatus according to claim 2, wherein the sensor is an encoder that outputs a pulse of a transport speed of a print recording medium transported by the transport belt as the synchronization signal. 4. The ink jet recording apparatus according to claim 2, further comprising a unit configured to detect an origin of the transport belt by the sensor.

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